Hydraulic anchor for oilfield service and method of using the same

Abstract

A hydraulic tubing anchor used in hydrocarbon producing wells has structure which positively contains a live slip within the mandrel of the anchor, thereby preventing the live slip from separating from the tubing anchor and dropping deeper into the well. Structure at the ends of the live slip engage within corresponding grooves of the slip recess.

What is claimed is: 
     
       1. In a hydrocarbon producing well having a length of well casing, a device restrains axial motion of a string of tubing within the length of well casing, the device comprising:
 a mandrel having an upper end, a lower end, and a plurality of axially oriented slip recesses spaced circumferentially about the mandrel, the slip recesses comprising a fixed slip recess and a live slip recess; 
 a fixed slip attached within the fixed slip recess, and a live slip disposed within the live slip recess; 
 the live slip recess comprising, with respect to the upper end and lower end of the mandrel, an upper end and a lower end, a first groove in the upper end and a second groove in the lower end, the first groove having a first width and the second groove having a second width, the live slip recess further comprising a cylindrical piston housing; 
 the live slip comprising a top end and a bottom end, the top end comprising a first axially extending tab and the bottom end comprising a second axially extending tab, wherein the first axially extending tab is disposed within the first groove and the second axially extending tab is disposed within the second groove; and 
 the first axially extending tab having a first thickness and the second axially extending tab having a second thickness wherein a range of travel of the live slip normal to a long axis of the mandrel is defined by the difference between the first width and the first thickness and the difference between the second width and the second thickness. 
 
     
     
       2. The device of  claim 1  wherein the live slip recess further comprises a pair of opposite facing arcuate slip shoulders, the cylindrical piston housing disposed between the opposite facing arcuate slip shoulders. 
     
     
       3. The device of  claim 2  wherein a first slip shoulder comprises the first groove and a second slip shoulder comprises the second groove. 
     
     
       4. The device of  claim 3  wherein the first groove and the second groove define a bend having a curvature concentric to the curvature of the cylindrical piston housing. 
     
     
       5. The device of  claim 1  wherein the mandrel comprises a fluted exterior surface. 
     
     
       6. In a hydrocarbon producing well having a length of well casing, a device restrains axial motion of a string of tubing within the length of well casing, the device comprising:
 a mandrel having an upward end and a downward end, wherein an axis is defined between the upward and the downward end, the mandrel adapted to be installed in-line in the string of tubing; 
 the mandrel comprising a continuous axial opening between the upper end and the downward end, the mandrel further comprising an exterior having a plurality of axially oriented slip recesses spaced circumferentially about the exterior, the slip recesses comprising at least two fixed slip recesses and a live slip recess, the live slip recess comprising an interior; 
 a fixed slip attached within each of the at least two fixed slip recesses; 
 the live slip recess comprising a cylindrical piston housing extending into the interior, the live slip recess further comprising a pair of opposite facing arcuate slip shoulders, the piston housing disposed between the opposite facing slip shoulders, wherein each slip shoulder comprises a arcuate groove facing the piston housing, each arcuate groove defining a bend having a curvature concentric to the curvature of the cylindrical piston housing; 
 a live slip disposed within the live slip recess, the live slip comprising an inward facing side, an outward facing side, an upper end and a lower end, wherein the inward facing side comprises a piston engagement surface in facing relation with the cylindrical piston housing and the upper end and the lower end each comprise an axially extending tab, each axially extending tab disposed within a corresponding arcuate groove of the respective slip shoulder, wherein each tab has an arcuate end having a curvature generally corresponding to the curvature of the arcuate groove in which the tab is disposed; and 
 a piston disposed within the cylindrical piston housing, where the piston is retained within the cylindrical piston housing by the piston engagement surface of the live slip. 
 
     
     
       7. The device of  claim 6  wherein the mandrel comprises a fluted exterior surface. 
     
     
       8. The device of  claim 7  wherein the exterior of the mandrel defines a circle. 
     
     
       9. The device of  claim 6  wherein the piston operates as a piston unit comprising the piston, a seal cup, an anchor ring, and an o-ring. 
     
     
       10. In a hydrocarbon producing well having a length of well casing, a method for restraining axial motion of a string of tubing within the length of well casing, the method comprising:
 installing a first part of the string of tubing into the well; 
 making up a tubing anchor in-line with the string of tubing; 
 installing a second part of the string of tubing into the well; 
 filling the string of tubing with liquid; 
 wherein the tubing anchor comprises (i) a mandrel having an upper end, a lower end, and a plurality of axially oriented slip recesses spaced circumferentially about the mandrel, the slip recesses comprising a fixed slip recess and a live slip recess wherein the live slip recess comprises a cylindrical piston housing; (ii) a fixed slip attached within the fixed slip recess, and the live slip disposed within the live slip recess; (iii) the live slip recess comprising, with respect to the upper end and lower end of the mandrel, an upper end and a lower end, a first groove in the upper end and a second groove in the lower end, the first groove having a first width and the second groove having a second width; (iv) the live slip comprising a top end and a bottom end, the top end comprising a first axially extending tab and the bottom end comprising a second axially extending tab, wherein the first axially extending tab is disposed within the first groove and the second axially extending tab is disposed within the second groove; and (v) the first axially extending tab having a first thickness and the second axially extending tab having a second thickness and a range of travel of the live slip normal to a long axis of the mandrel is defined by the first thickness with respect to the first width and the second thickness with respect to the second width. 
 
     
     
       11. The method of  claim 10  comprising the further step of installing a rod string and a pump. 
     
     
       12. The method of  claim 10  wherein the live slip recess further comprises a pair of opposite facing arcuate slip shoulders, the cylindrical piston housing disposed between the opposite facing arcuate slip shoulders. 
     
     
       13. The method of  claim 12  wherein a first slip shoulder comprises the first groove and a second slip shoulder comprises the second groove. 
     
     
       14. The method of  13  wherein the first groove and the second groove define a bend having a curvature concentric to the curvature of the cylindrical piston housing. 
     
     
       15. The method of  claim 14  wherein the mandrel comprises a fluted exterior surface. 
     
     
       16. In a hydrocarbon producing well having a length of well casing, a device restrains axial motion of a string of tubing within the length of well casing, the device comprising:
 a mandrel having an exterior, an interior, an upper end, a lower end, and a plurality of axially oriented slip recesses spaced circumferentially about the exterior of the mandrel, the slip recesses comprising a fixed slip recess and a live slip recess; 
 a fixed slip attached within the fixed slip recess, and a live slip disposed within the live slip recess; 
 the live slip recess comprising, a generally flat section disposed between an upper arcuate slip shoulder and a lower arcuate slip shoulder, the upper arcuate slip shoulder and the lower arcuate slip shoulder in facing relation; 
 a cylindrical piston housing disposed on the generally flat section, the cylindrical piston housing having a circular opening extending into the interior; 
 the upper arcuate slip shoulder comprising a first arcuate lip section which overhangs the generally flat section, wherein a first groove is defined between the first arcuate lip section and the generally flat section; 
 the lower arcuate slip shoulder comprising a second arcuate lip section which overhangs the generally flat section, wherein a second groove is defined between the second arcuate lip section and the generally flat section; 
 the live slip comprising an outwardly facing surface and inwardly facing surface, the inwardly facing surface comprising a piston engagement surface, the live slip further comprising a top end and a bottom end, the top end comprising a first axially extending tab and the bottom end comprising a second axially extending tab, wherein the first axially extending tab is disposed within the first groove and the second axially extending tab is disposed within the second groove; and 
 a piston disposed within the cylindrical piston housing, where the piston is retained within the cylindrical piston housing by the piston engagement surface of the live slip. 
 
     
     
       17. The device of  claim 16  wherein the first groove has a first width and the second groove has a second width, and the first axially extending tab has a first thickness and the second axially extending tab has a second thickness and a range of travel of the live slip normal to a long axis of the mandrel is defined by the first thickness with respect to the first width and the second thickness with respect to the second width. 
     
     
       18. The device of  claim 16  wherein each groove defines a bend having a curvature concentric to the cylindrical piston housing.